After my visit to Marblehead, I commented briefly on the common practice of using a single vertical stroke to carve two adjacent letters on 17th-century gravestones.
I have never seen a better example of this than the Sampson Waters stone (1693) at Copp's Hill. Of the 16 words on this stone, six include shared uprights. The Sampson Waters stone is a fairly small stone with very wide borders and a reduced space for the inscription. I don't know for sure, but this suggests that sharing vertical lines was mostly a matter of conserving space.
The funny thing is, shared uprights are often difficult to spot. It's like those passages that show that letter order and vowels aren't all that important for reading comprehension — when you're reading, your eyes skip right over the shared parts and just make the letters appear. Look at the word "Sampson." Unless you concentrate, the "p" looks perfectly normal.
Several other stones at Copp's Hill use the shared upright trick. As far as I can tell, they are not all carved by the same person, but most seem to have been carved before 1720 or so.